ADVANCED ISLANDING DETECTION METHODS FOR SINGLE PHASE GRID CONNECTED PV INVERTERS

Due to the growing concerns associated with fossil fuels, emphasis has been placed on clean and sustainable energy generation. This has resulted in the increase in Photovoltaics (PV) units being integrated into the utility system. The integration of PV units has raised some concerns for utility power systems, including the consequences of failing to detect islanding. Numerous methods for islanding detection have been introduced in literature. They can be categorized into local methods and remote methods. The local methods are categorically divided into passive and active methods. Active methods generally have smaller Non-Detection Zone (NDZ) but the injecting disturbances will slightly degrade the power quality and reliability of the power system. Slip Mode Frequency Shift Islanding Detection Method (SMS IDM) is an active method that uses positive feedback for islanding detection. In this method, the phase angle of the converter is controlled to have a sinusoidal function of the deviation of the Point of Common Coupling (PCC) voltage frequency from the nominal grid frequency. This method has a non-detection zone which means it fails to detect islanding for specific local load conditions. If the SMS IDM employs a different function other than the sinusoidal function for drifting the phase angle of the inverter, its non-detection zone could be smaller. In addition, Advanced Slip Mode Frequency Shift Islanding Detection Method (Advanced SMS IDM), which has been introduced in this thesis, eliminates the non-detection zone of the SMS IDM. In this method the parameters of SMS IDM change based on the local load impedance value. Moreover, the stability of the system is investigated by developing the dynamical equations of the system for two operation modes; grid connected and islanded mode. It is mathematically proven that for some loading conditions the nominal frequency is an unstable point and the operation frequency slides to another stable point, while for other loading conditions the nominal frequency is the only stable point of the system upon islanding occurring. Simulation and experimental results show the accuracy of the proposed methods in detection of islanding and verify the validity of the mathematical analysis.

The political economy of industrial policy in Peru and Ecuador: 1980-2010

This dissertation focuses on industrial policy in two developing countries: Peru and Ecuador. Informed by comparative historical analysis, it explains how the Import-Substitution Industrialization policies promoted during the 1970s by military administration unravelled in the following 30 years under the guidance of Washington Consensus policies. Positioning political economy in time, the research objectives were two-fold: understanding long-term policy reform patterns, including the variables that conditioned cyclical versus path-dependent dynamics of change and; secondly, investigating the direction and leverage of state institutions supporting the manufacturing sector at the dawn, peak and consolidation of neoliberal discourse in both countries. Three interconnected causal mechanisms explain the divergence of trajectories: institutional legacies, coordination among actors and economic distribution of power. Peru’s long tradition of a minimal state contrasts with the embedded character of Ecuador long tradition of legal protectionism dating back to the Liberal Revolution. Peru’s close policy coordination among stakeholders –state technocrats and business elites- differs from Ecuador’s “winners-take-all” approach for policy-making. Peru’s economic dynamism concentrated in Lima sharply departs from Ecuador’s competitive regional economic leaderships. This dissertation paid particular attention to methodology to understand the intersection between structure and agency in policy change. Tracing primary and secondary sources, as well as key pieces of legislation, became critical to understand key turning points and long-term patterns of change. Open-ended interviews (N=58) with two stakeholder groups (business elites and bureaucrats) compounded the effort to knit motives, discourses, and interests behind this long transition. In order to understand this amount of data, this research build an index of policy intervention as a methodological contribution to assess long patterns of policy change. These findings contribute to the current literature on State-market relations and varieties of capitalism, institutional change, and policy reform.